Drive machine for elevators with drive sheave position detector

ABSTRACT

A drive machine for elevators includes a rotatable drive sheave over which a main cable for hanging an elevator cage is wound, a stationary shaft for supporting rotation of the drive sheave and bearing a load applied to the drive sheave from the main cable, a field magnet attached to the drive sheave, constituting a part of an electric motor, and including at least one pair of magnetic poles, an armature attached to the stationary shaft facing the field magnet and constituting another part of the motor, and a field magnetic pole detector for detecting a magnetic pole of the field magnet rotating together with the drive sheave.

TECHNICAL FIELD

The present invention relates to an elevator apparatus, and moreparticularly to a drive machine for elevators which employ an outerrotor motor.

BACKGROUND ART

FIGS. 11 and 12 show a conventional elevator apparatus disclosed in, forexample, Japanese Unexamined Patent Publication No. 7-117957. Thedisclosed elevator apparatus is of the traction sheave type wherein amain cable is wound over a drive sheave, and a cage and a counterweightare moved up and down in opposite directions. The elevator apparatusemploys, as a winder, an outer rotor motor. FIG. 11 is a perspectiveview of the elevator apparatus, and FIG. 12 is an enlarged sectionalview of a drive machine shown in FIG. 11.

Referring to FIGS. 11 and 12, denoted by numeral 1 is an elevator pit, 2is a cage, 3 is a cage guide rail vertically provided as a pair withinthe elevator pit 1 for guiding both sides of the cage 2 so that the cagemoves up and down along a predetermined path, 4 is a counterweight, 5 isa counterweight guide rail vertically provided as a pair within theelevator pit 1 for guiding both sides of the counterweight 4 so that thecounterweight moves up and down along a predetermined path, and 6 is abraking device associated with the counterweight 4 and tightly pressedagainst the counterweight guide rails 5 for applying a brake as theoccasion requires. Numeral 7 denotes a support beam provided at the topof the elevator pit 1, and 8 denotes a winder comprising an outer rotormotor provided at the top of the elevator pit 1.

As shown in FIG. 12, the winder 8 mainly comprises a stationary shaft 9having opposite ends supported by and fixed to the support beams 7, anarmature iron-core 11 fixed to the shaft 9 and having armature coils 10wound over the same, and a rotor 12 rotatably supported by the shaft 9and constituting a drive sheave.

The rotor 12 includes a field iron-core 13, a field permanent magnet 14,a drive sheave 16 having cable grooves formed in its outer periphery,and bearings 17 disposed between the rotor and the shaft 9 for rotatablysupporting the former relative to the latter. Numeral 18 denotes anelevator main cable wound along the sheave groove 15, the main cablehaving one end coupled to the cage 2 and the other end coupled to thecounterweight 4. Numeral 19 denotes a braking device associated with therotor 12 for stopping the rotor 12.

Numeral 20 denotes an absolute value encoder in the form of a ring. Theabsolute value encoder 20 is arranged such that it surrounds a projectedflange of the rotor 12, is joined to the projected flange of the rotor12 through a bearing 21 for free rotation of the rotor 12, and is fixedthrough a mounting fixture 23 to an encoder holder 22 which is securedto the shaft 9. Numeral 24 denotes a supporting fixture provided on eachof the support beams 7 on both sides for supporting the shaft 9.

In the drive machine thus constructed, the magnetic pole position of thefield permanent magnet 14 is detected by the absolute value encoder 20,and the phases of currents supplied to the armature coils 10 arecontrolled in accordance with the detected result. Also, the rotatingspeed and the rotating direction of the rotor 12 and hence the drivesheave 16 are detected by the absolute value encoder 20 in order tocontrol the rising/lowering speed and the moving direction of the cage2.

In not only such a synchronous motor using a field permanent magnet, butalso other electric motors such as the so-called three-phase inductionmotor, it is important to detect the rotational angle of a rotor withrespect to a field magnet in a circuit driving control for any of thosemotors.

The above-described conventional drive machine for elevators hasproblems below. Supposing, for example, that the absolute value encoder20 directly attached to the shaft of the winder malfunctions and has tobe replaced, because the absolute value encoder 20 is in the ring form,it is required to dismount the entirety of the winder 8 by moving theshaft 9 upward so as to be withdrawn from the supporting fixtures 24fixed to the support beams 7, thus resulting in troublesome work. Inaddition, when the winder 8 is mounted at the top of the elevator pit 1,scaffolding must be temporarily built up, which renders the replacementwork more troublesome.

Further, because the absolute value encoder 20 is in the ring form andarranged in a surrounding relation to the projected flange of the rotor12, its inner diameter is so large that an inexpensive absolute valueencoder, which is usually employed in general motors having rotaryshafts, is not usable. This raises another problem that the absolutevalue encoder 20 must be a custom and expensive product.

Still another problem is that because the magnetic pole position of thefield magnet is indirectly determined by the absolute value encoder 20surrounding the projected flange of the rotor 12, the accurate magneticpole position of the field magnet cannot be obtained.

The present invention has been accomplished with the view of solvingthe-problems set forth above, and its object is to provide a drivemachine for elevators which can determine the accurate magnetic poleposition of a field magnet, and can facilitate maintenance work for adetecting unit to detect the magnetic pole position, the rotating speedand the rotating direction of the field magnet.

DISCLOSURE OF THE INVENTION

A first aspect of the present invention resides in a drive machine forelevators, which comprises a rotatable drive sheave over which a maincable for hanging an elevator cage is wound, a stationary shaft forsupporting rotation of the drive sheave and bearing a load applied tothe drive sheave from the main cable, a field magnet attached to thedrive sheave, constituting a part of an electric motor, and comprisingat least one pair of magnetic poles, an armature attached to thestationary shaft in a facing relation to the field magnet andconstituting another part of the motor, and a field magnetic poledetector for detecting the predetermined magnetic pole of the fieldmagnet rotated together with the drive sheave.

A second aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the first aspect, that thefield magnet comprises a permanent magnet.

A third aspect-of the present invention resides in, on the basis of thedrive machine for elevators according to the first or second aspect,that the field magnetic pole detector comprises a magnetic sensorattached to the stationary side in a close and facing relation to thefield magnet.

A fourth aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the first aspect, that adetected portion indicating the position of the magnetic pole disposedon the drive sheave is provided on the drive sheave in a facing relationto the field magnetic pole detector, and the position of thepredetermined magnetic pole is recognized with the field magnetic poledetector detecting the detected portion.

A fifth aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the fourth aspect, that thedetected portion comprises a convex or concave portion formed on or inthe surface of the drive sheave corresponding to the position of thepredetermined magnetic pole.

A sixth aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the first aspect, that thefield magnetic pole detector is provided at least three at a pitch equalto {fraction (1/3+L )} of the pitch of one pair of the field magneticpoles.

A seventh aspect of the present invention resides in, on the basis ofthe drive machine for elevators according to the second or sixth aspect,further comprising a rotation detector for detecting rotation of thedrive sheave with respect to the stationary shaft as a reference, anddrive control means for executing drive control of the motor inaccordance with results detected by the rotation detector and the fieldmagnetic pole detector, wherein the drive control means starts up themotor in accordance with an imaginary field magnetic pole position whenthe magnetic pole position of the field magnet attached to the drivesheave is not known at the start-up of the elevator, and executes thedrive control in accordance with the results detected by the fieldmagnetic pole detector and the rotation detector after the fieldmagnetic pole position has been recognized upon operation of the fieldmagnetic pole detector.

An eighth aspect of the present invention resides in, on the basis ofthe drive machine for elevators according to the first aspect, furthercomprising a rotation detector for detecting rotation of the drivesheave with respect to the stationary shaft as a reference, detectiondifference calculating means for detecting the difference between therotation of the drive sheave detected by the rotation detector and therotation of the drive sheave detected by the field magnetic poledetector, and anomaly determining means for determining the occurrenceof an anomaly when a value of the difference determined by the detectiondifference calculating means exceeds a predetermined value.

A ninth aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the eighth aspect, furthercomprising drive control means for executing drive control of the motorin accordance with results detected by the rotation detector and thefield magnetic pole detector, wherein when the value of the differencedetermined by the detection difference calculating means does not exceedthe predetermined value, the drive control means executes the controlwhile correcting an output value of the rotation detector in accordancewith the value of the difference.

A tenth aspect of the present invention resides in, on the basis of thedrive machine for elevators according to the first aspect, furthercomprising a rotation detector for detecting rotation of the drivesheave with respect to the stationary shaft as a reference, memory meansfor storing an output of the rotation detector in a correspondingrelation to the position detected by the field magnetic pole detectorwhile the field magnetic pole detector is detecting the field magneticpole position with the rotation of the drive sheave, and drive controlmeans for executing drive control of the motor in accordance withresults detected by the rotation detector and the field magnetic poledetector, wherein the drive control means utilizes values stored in thememory means for phase control of electric power supplied to thearmature.

An eleventh aspect of the present invention resides in, on the basis ofthe drive machine for elevators according to the first aspect, furthercomprising a rotation detector for detecting rotation of the drivesheave with respect to the stationary shaft as a reference, and drivecontrol means for executing drive control of the motor in accordancewith results detected by the rotation detector and the field magneticpole detector, wherein the amount of change in value detected by therotation detector is determined at the start-up of the elevator whilethe field magnetic pole detector detects one pair of the field magneticpoles, and the drive control means executes phase control of the motorby setting the amount of change as a reference value of a phase signalfor one pair of the field magnetic poles since then.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional view showing a structure of a drive machine forelevators according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view taken along the line II—II of FIG. 1.

FIG. 3 is a chart showing the correlation between the positions ofproximity switches shown in FIG. 2 and signals from the proximityswitches.

FIG. 4 is a sectional view showing a structure of a drive machine forelevators according to Embodiment 2 of the present invention.

FIG. 5 is a sectional view taken along the line V—V of FIG. 4.

FIG. 6 is a block diagram showing inverter control in drive machineaccording to Embodiments 3 and 4 of the present invention.

FIG. 7 is a waveform chart for explaining the operation of Embodiment 3of the present invention.

FIG. 8 is a waveform chart for explaining another operation ofEmbodiment 3 of the present invention.

FIG. 9 is a waveform chart for explaining still another operation ofEmbodiment 3 of the present invention.

FIG. 10 is a waveform chart for explaining the operation of Embodiment 4of the present invention.

FIG. 11 is a perspective view of a conventional elevator apparatusincluding a winder which comprises an outer rotor.

FIG. 12 is a sectional view showing a structure of a conventional drivemachine for elevators which comprises an outer rotor.

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

FIG. 1 is a sectional view showing a structure of a drive machine forelevators according to one embodiment of the present invention. In FIG.1, the same or corresponding parts as or to those in the conventionaldrive machine described above are denoted by the same symbols.

A winder 8 mainly comprises a stationary shaft 9 having opposite endssupported by supporting fixtures 24, an armature iron-core 11 (armature)having armature coils 10 wound over the same, and a rotor 12 rotatablysupported by the shaft 9 and constituting a drive sheave 16. Note that 0denotes an axis of the shaft 9.

The rotor 12 includes a field permanent magnet 14 (field magnet)disposed inside the rotor to face the armature iron-core 11, cablegrooves 15 formed in an outer periphery of the rotor for receiving amain cable 18 wound over the rotor, and machined portions 30 (detectedportions) in the form of recesses which are used to detect the magneticpole position of the field permanent magnet 14. Additionally, bearings17 are disposed between the rotor 12 and the shaft 9.

While the winder utilizing the permanent magnet 14 as a field magnet isdescribed here, the present invention is also similarly applicable toanother type of winder wherein an iron core having coils wound aroundthe same is disposed (not shown) in place of the permanent magnet, andelectric power is supplied to the coils through a slip ring, therebygenerating a magnetic field as with the permanent magnet.

Further, around the winder 8, there are provided proximity switches 27as field magnetic pole detectors for detecting the position of eachmachined portion 30 in the form of a recess, and a rotary encoder 29serving as a rotation detector and including a roller 28 held pressedagainst the outer periphery of the rotor 12 for detecting the rotatingspeed and the rotating direction of the rotor 12. Numeral 25 denotes amounting stand for the rotary encoder 29. The proximity switches 27 maybe attached to the mounting stand 25, or may be attached to a dedicatedmounting stand (not shown) which is provided separately.

FIG. 2 is a sectional view taken along the line II—II of FIG. 1, showingthe positional relationship among the machined portion 30 in the form ofa recess, the field permanent magnet 14, and the proximity switches 27a-27 c. Referring to FIG. 2, the outer periphery of the rotor 12 ismachined to have a recess (30) in a position coincident with theposition of each N pole of the field permanent magnet 14 where the poleis fixed to the rotor 12, as viewed from the center LO of the rotatingshaft in the radial direction, while the rotor outer periphery is notmachined to have a recess in a position coincident with the position ofeach S pole where it is fixed to the rotor 12.

To detect the positions of the concave and convex machined portions 30formed in the outer periphery of the rotor 12, three proximity switches27 a-27 c are mounted in a close relation to the concave and convexmachined portions 30. Supposing that an angle occupied by one pair of Nand S poles of the field permanent magnet 14 is α, the proximityswitches 27 a-27 c are arranged along the outer periphery of the rotor12 in such positions that the interval (pitch) between the proximityswitches is α/3.

Next, how respective signals from the proximity switches 27 a-27 cchange depending on their relative positions to the concave and convexmachined portions 30 will be described in conjunction with FIG. 3. Forthe convenience of explanation, the positions of the concave and convexportions and the magnets, and the mount positions of the proximityswitches are represented in the linear form.

When the concave and convex portions are moved from the position shownin FIG. 3 in the direction of arrow S, the signals from the proximityswitches 27 a-27 c change as shown, namely change in six combinationsP1-P6, while the rotor moves through the angle a corresponding to onepair of the concave and convex portions. After that, the signals fromthe proximity switches 27 a-27 c change in the same manner repeatedly.Since the concave and convex portions are positioned in a one-to-onerelation to the magnetic poles, α is given by 360 degrees representingone cycle of the magnetic pole phase, and therefore P1 to P6 eachrepresent a range of 60 degrees. In other words, the magnetic poleposition can be determined based on the combinations in state of thesignals from the proximity switches 27 a-27 c with resolution of 60degrees.

As well known, a synchronous motor of the type employing a permanentmagnet cannot start up unless the magnetic pole position of a fledmagnet is known at the time of start-up. With the method according tothis Embodiment, the magnetic pole position can be detected with anangular range of 60 degrees. Assuming that the magnetic pole positionlocates at the middle of the 60-degree range, an error between theactual magnetic pole position and the measured magnetic pole position is±30 degrees at maximum. When the synchronous motor of the type employinga permanent magnet is operated under vector control, a torque reductionof 13% occurs at a maximum error because of cos30°=0.87, but asufficient torque for the start-up can be generated. Once the rotor 12is rotated and a level of the signal from any-one of the proximityswitches 27 a-27 c is changed over, the magnetic pole position can beprecisely detected at that time, and current phase control can beperformed with a highly-accurate magnetic pole position signal sincethen.

When later-described drive control means for the winder 8 in the form ofa motor, shown in FIG. 6, cannot know in which position the motorlocates relative to the corresponding field magnetic pole at thestart-up, i.e., when it is not known how far the motor has rotated,before stopping, from the changing-over point of the magnetic pole to bedetected, an imaginary position in the field magnet is introduced andphase control is performed in accordance with the imaginary position inthe field magnet until the first field magnetic pole detector startsoperation. By so doing, the drive sheave can be started up even if theposition in the field magnet is not known at the start-up.

Further, since the changing-over point between the concave and convexportions is coincident with the changing-over point between the magneticpoles, this provides such an advantage that the changing-over pointbetween the magnetic poles can be directly read based on the signalsfrom the proximity switches 27 a-27 c. On the other hand, the rotatingdirection and the rotating speed of the rotor 12 are determined based ona signal from the rotary encoder 29.

The concave and convex machined portions may be provided in any othersuitable locations than the outer periphery of the rotor. A similaroperating effect as-described above can be obtained if the concave andconvex machined portions are located in coincidence with the positionsof the magnetic poles of the field magnet as viewed from the center ofthe rotating shaft in the radial direction. The similar operating effectcan also be obtained by attaching a ring with concave and convexportions in coincidence with the magnetic pole positions rather thandirectly machining the rotor (drive sheave) to have the concave andconvex portions.

As described above, since the proximity switches 27 a 27 c serving asfield magnetic pole detectors and the rotary encoder 29 serving as arotation detector are arranged as separate components in an easilydetachable manner, it is easy to carry out check and displacement in theevent of failure.

Moreover, since the field magnetic pole position is directly detectedfrom the concave and convex machined portions 30 precisely correspondingto the field permanent magnet 14 which provides field magnetic poles,the winder can be controlled with good accuracy.

Second Embodiment

FIG. 4 is a sectional view showing a structure of a drive machine forelevators according to another embodiment of the present invention, andFIG. 5 is a sectional view taken along the line V—V of FIG. 4. Aprincipal part of this embodiment is the same as shown in FIGS. 1 and 2.This embodiment employs, as field magnetic pole detectors, threemagnetic sensors 70 a-70 c provided in the proximity of the fieldpermanent magnet 14. Numeral 71 denotes a mounting fixture for themagnetic sensors 70 a-70 c. The magnetic sensors 70 a-70 c obtaininformation about the position of a field magnet, i.e., the fieldmagnetic pole position, by directly detecting the magnetic fieldgenerated by the field permanent magnet 14.

With such an arrangement, since the magnetism generated by the fieldmagnet is directly detected by the magnetic sensors, the construction issimplified and the magnetic pole position can be more preciselyobtained. In addition, by combining the magnetic sensors with apermanent magnet to provide field magnetic poles, the position in thefield magnet can be roughly detected from the magnitude of detectedmagnetic flux even while the rotor is stopped.

Third Embodiment

A phase control method used in the case of detecting the rotation of thewinder 8 by the rotary encoder 29 using the roller 28, and detecting themagnetic pole position by separate magnetic pole position detectors, asdescribed in the above First and Second Embodiments, will be describedbelow with reference to FIGS. 6 and 7. FIG. 6 is a control block diagramof an inverter for driving the winder 8 which comprises a synchronousmotor of the outer rotor type employing a permanent magnet as a fieldmagnet. Note that an elevator control section, a position controlsection, etc., which are not directly related to the present invention,are omitted from the drawing.

In FIG. 6, the same or corresponding parts as or to those in the aboveEmbodiments are denoted by the same symbols. Numeral 43 denotes aninverter for driving the winder 8 which comprises an outer rotor motor,27 denotes a proximity switch for detecting the field magnetic poleposition within the winder 8, and 29 denotes a rotary encoder fordetecting the rotation of the winder 8 through the roller 28. Further,denoted by numeral 40 is a power supply, 41 is a converter, 42 is asmoothing capacitor, 2 is an elevator cage, and 4 is a counterweight.

Numeral 45 denotes a speed detecting section for determining the speedbased on a signal from the rotary encoder 29, 46 denotes a phasedetecting section for determining the current phase based on a signalfrom the rotary encoder 29, 47 denotes a magnetic pole positiondetecting section for determining the magnetic pole position based onsignals from the proximity switches 27, 49 denotes a speed controlsection for combining a speed command-and a speed feedback signal w tocalculate a torque current command iq, 50 denotes a current commandcreating section for calculating a current command from an excitationcurrent command id, the torque current command iq and a phase signal θ,and 51 denotes a current control section for combining the currentcommand and a current detection signal from a current sensor 44 tooutput a control signal to the inverter 43.

Numeral 55 denotes memory means for storing, in a correlated manner, thecurrent phase, i.e., the position in the field magnet, determined by thephase detecting section 46 based on the signal from the rotary encoder29, and the magnetic pole position recognized by the magnetic poleposition detecting section 47 based on the signals detected by theproximity switches 27. Numeral 56 denotes detection differencecalculating means for determining the difference between the magneticpole position recognized by the magnetic pole position detecting section47 based on the signals detected by the proximity switches 27 and themagnetic pole position determined by the phase detecting section 46based on the signal from the rotary encoder 29. Numeral 57 denotesanomaly determining means for generating an abnormal signal upondetermining the occurrence of an anomaly if the difference or deviationin the magnetic pole position resulted from the different detectors anddetermined by the detection difference calculating means 56 exceeds apredetermined value.

A manner of determining the phase signal θ will now be described withreference to FIG. 7. In FIG. 7, alphabet A represents an initial stateimmediately after power-on, and the phase signal 6 is set to a phasesignal θA that is determined from a combination of the signals from thethree proximity switches 27 in accordance with the above-describedmethod. Subsequently, when the winder 8 is rotated and a pulse signal isoutputted from the rotary encoder 29 with the rotation of the winder 8,the phase detecting section 46 counts the number of the pulses, andoutputs the phase signal 8 after multiplying the counted number by aphase angle corresponding to one pulse. Further, in the synchronousmotor, the current phase signal θ must be coincident with the cycle ofthe magnetic pole position of the field magnet.

To that end, the phase signal θ is reset to be coincident with 0 degree,for example, at the changing-over point from the S to N pole of themagnetic pole position signal determined based on the signals from theproximity switches 27, as shown in FIG. 7.

As shown in FIG. 8, however, the length of one cycle of each detectorsignal may change due to errors in machining of the concave machinedportions 30 serving as the detected portions in Embodiment 1, or errorsin installation of the proximity switches 27 a-27 c used in Embodiment 1and the magnetic sensors 70 a-70 c used in Embodiment 2 which serves asthe field magnetic pole detectors. If the length of one cycle isshortened, for example, the phase signal θ is reset to 0 degree beforereaching 360 degrees. Conversely, if the length of one cycle isprolonged, the phase signal θ is reset midway the succeeding cycle. Thisresults in that the phase signal θ becomes not consistent and the motorcannot rotate smoothly.

To cope with the above-mentioned problem, the length corresponding toeach cycle of the magnetic poles is stored as the difference in countedvalue of the output pulses from the rotation detector (rotary encoder29) over the entire circumference of the winder 8. Thus, a time period(a) in FIG. 8 is represented by a value of C2-C1, a time period (b) by avalue of C3-C2, and a time period (c) by a value of C4-C3.

In a shorter time period, e.g., the time period (b), than the standardone (a), the amount of change in value of the phase signal θcorresponding to one count of the output pulses from the rotationdetector is calculated from the stored pulse counted values, and is setto be larger than in the standard time period to modify the value of thephase signal θ so that one cycle completes at 360 degrees. Conversely,in a longer time period, e.g., the time period (c), than the standardone (a), the amount of change in value of the phase signal θ is set tobe smaller than in the standard time period to modify the value of thephase signal θ so that one cycle completes at 360 degrees. Statedotherwise, as shown in FIG. 8, while the phase signal θ has the sameslope for each time period in the unmodified case, the slope of thephase signal θ is changed depending on the stored length of one cycle inthe modified case. With such a modification, the value of the phasesignal θ is kept from becoming inconsistent, and smooth phase controlcan be achieved.

The operation in the above case will be described below with referenceto FIG. 6. After the winder 8 has started up, the magnetic pole positiondetecting section 47 detects the changing-over point in the cycle of themagnetic poles, and assigns the successive number to each cycle from thefirst cycle over a full turn. At the same time, the assigned numbers andthe difference in counted value of the output pulses from the rotaryencoder 29 for each cycle are stored in the storage means 55. Afterthat, the magnetic pole position detecting section 47 outputs, to thephase detecting section 46, information indicating in what number ofmagnetic pole cycle the winder 8 is positioned at this moment. Inaccordance with the indicated number of magnetic pole cycle, the phasedetecting section 46 reads the difference in counted value of thecorresponding magnetic pole cycle from the storage means 55, anddetermines the length of the cycle. Then, in consideration ofcorrespondence between the signal newly inputted from the rotary encoder29 and the length of the cycle, the phase detecting section 46 modifiesand calculates the phase signal θ so that one cycle completes at 360degrees. The modified phase signal θ is outputted to the current commandcreating section 50.

On the other hand, because the rotation of the winder 8 is detected bythe rotary encoder 29 using the roller 28, there is a possibility thatslippage of the roller may occur. The function of detecting such aslippage and the function of generating an abnormal signal will now bedescribed with reference to FIG. 9.

If the rotation of the rotary encoder 29 becomes slower than therotation of the winder 8 due to slippage of the roller 28 during theoperation, the phase signal θ deviates by a large amount from 360degrees at the changing-over point of the magnetic pole position signalas indicated by X in FIG. 9. In view of such a problem, at thechanging-over point from the S to N pole of the magnetic pole positionsignal from the magnetic pole position detecting section 47, thedetection difference calculating means 56 determines how far the phasesignal θ from the phase detecting section 46 deviates from 0 degree or360 degrees. Then, the anomaly determining means 57 sets an angle of acertain width d at the changing-over point from the S to N pole of themagnetic pole position signal from the magnetic pole position detectingsection 47 as shown in FIG. 9, and monitors whether the angle of thephase signal θ from the phase detecting section 46 deviates over theangle d not, thereby outputting an abnormal signal if the deviation overthe angle d occurs. The width of d is set to about 10 degrees in termsof phase angle, taking into account that a torque reduction should notbe so increased and that a speed detection error should not be soenlarged.

Further, when the rotation of the winder 8 is sped up, there also occursan error in the magnetic pole position signal due to a delay inoperation of the proximity switches 27. Since this error is proportionalto the speed, the speed feedback signal ω is applied to the magneticpole position detecting section 47 which creates the magnetic poleposition signal after compensating for the error in accordance with thespeed feedback signal ω. This process increases the accuracy indetecting slippage of the roller. On the other hand, a response speed ofthe rotary encoder 29 is sufficiently high and a delay in operationthereof is negligible.

Fourth Embodiment

When the rotation of the winder 8 is detected by the rotary encoder 29using the roller 28 like the above Embodiment 1, the roller 28 may beabraded to cause a change of configuration over time and hence toproduce an error in the phase signal θ. Supposing, for example, that theroller 28 has a diameter of 100 mm and the length of one pair ofmagnetic poles of the field permanent magnet 14 is exactly equal to{fraction (1/2+L )} of the outer circumference of the roller 28, if theroller 28 is abraded 0.1 mm and the diameter is changed to 99.8 mm, thephase signal θ would shift 90 degrees in terms of the magnetic polephase after only 62.5 rotations of the roller 28. The 90-degree shift ofthe magnetic pole phase means that the torque applied to the winder 8becomes zero.

To cope with that problem, as shown in FIG. 10, immediately after thestart-up of the winder 8, the number of output pulses from the rotaryencoder 29 is counted (a value given by PB−PA in the drawing) for onecycle of the signal from the proximity switch 27 (indicated by thesignal from 27 a in the drawing), and the counted value is used as areference value for-one cycle of the magnetic pole phase in thesubsequent phase calculation until the winder 8 is stopped. Since thelength of one pair of magnetic poles of the field permanent magnet 14 isfixed regardless of the roller abrasion, the pulse count for one cycleof the magnetic pole phase can be correctly detected even if the rollerdiameter varies due to a change of configuration over time. As analternative, counting the number of pulses over several cycles andcalculating an average of the counted numbers as a standard valuefurther increases the accuracy. Such a modification can be easilyimplemented, for example, by adding a correcting section 46 a, which hasthe calculating and storing functions and the temporarily storingfunction required for the modified process, to the phase detector 46shown in FIG. 6.

Industrial Applicability

As described above, according to the first aspect of the presentinvention, a drive machine for elevators comprises a rotatable drivesheave over which a main cable for hanging an elevator cage is wound, astationary shaft for supporting rotation of the drive sheave and bearinga load applied to the drive sheave from the main cable, a field magnetattached to the drive sheave, constituting a part of an electric motor,and comprising at least one pair of magnetic poles, an armature attachedto the stationary shaft in a facing relation to the field magnet andconstituting another part of the motor, and a field magnetic poledetector for detecting the predetermined magnetic pole of the fieldmagnet rotated together with the drive sheave. With the provision of thefield magnetic pole detector capable of directly and precisely detectingthe position in the field magnet, rotational angle control of the drivesheave and control of the motor can be implemented with good accuracy.

According to the second aspect of the present invention, on the basis ofthe first aspect, the field magnet comprises a permanent magnet. If afield magnet using winding coils is attached to the rotatable drivesheave, a special device such as a slip ring is required to supplyexcitation currents to the coils. By contrast, the use of a permanentmagnet eliminates the need of such a special device.

According to the third aspect of the present invention, on the basis ofthe first or second aspect, the field magnetic pole detector comprises amagnetic sensor attached to the stationary side in a close and facingrelation to the field magnet. Therefore, the magnetism generated by thefield magnet can be directly detected by the magnetic sensor, and hencethe construction is simplified. In addition, by combining the magneticsensor with the use of the above permanent magnet, the position in thefield magnetic can be roughly detected from the magnitude of detectedmagnetic flux even while the motor is stopped.

According to the fourth aspect of the present inventions on the basis ofthe first aspect, a detected portion indicating the position of themagnetic pole disposed on the drive sheave is provided on the drivesheave in a facing relation to the field magnetic pole detector, and theposition of the predetermined magnetic pole is recognized with the fieldmagnetic pole detector detecting the detected portion. With thisfeature, an optimum detected portion adapted for the field magnetic poledetector can be provided on the drive sheave, and the detecting positioncan be set with good accuracy and high flexibility.

According to the fifth aspect of the present invention, on the basis ofthe fourth aspect, the detected portion comprises a convex or concaveportion formed on or in the surface of the drive sheave corresponding tothe position of the predetermined magnetic pole. By simply machining aportion of a body of the drive sheave in synch with the magnetic poleposition of the field magnet attached to the drive sheave, therefore,the detected portion can be formed without intricate machining andadditional parts to constitute special detected means.

According to the sixth aspect of the present invention, on the basis ofthe-first aspect, the field magnetic pole detector is provided at leastthree at a pitch equal to {fraction (1/3+L )} of the pitch of one pairof the field magnetic poles. Therefore, the field magnetic pole positioncan be recognized with resolution of 60 degrees by only the fieldmagnetic pole detectors. In other words, the field magnetic poleposition can be detected by a small number of field magnetic poledetectors. In addition, even the resolution of 60 degrees corresponds toa torque error less than 15% in control of the motor, and is within theallowable range from the viewpoint of control capability.

According to the seventh aspect of the present invention, on the basisof second or sixth aspect, the drive machine for elevators furthercomprises a rotation detector for detecting rotation of the drive sheavewith respect to the stationary shaft as a reference, and drive controlmeans for executing drive control of the motor in accordance withresults detected by the rotation detector and the field magnetic poledetector, wherein the drive control means starts up the motor inaccordance with an imaginary field magnetic pole position when themagnetic pole position of the field magnet attached to the drive sheaveis not known at the start-up of the elevator, and executes the drivecontrol in accordance with the results detected by the field magneticpole detector and the rotation detector after the field magneticpole-position has been recognized upon operation of the field magneticpole detector. With this feature, when the drive control means cannotknow in which position the motor locates relative to the correspondingfield magnetic pole at the start-up, i.e., when it is not known how farthe motor has rotated, before stopping, from the point to be detected(the changing-over point of the field magnetic pole), the imaginaryfield magnetic pole position is introduced and phase control isperformed in accordance with the imaginary field magnetic pole positionuntil the first field magnetic pole detector starts operation. Thus, thedrive sheave can be started up even if the position in the field magnetis not known at the startup.

According to the eighth aspect of the present invention, on the basis ofthe first aspect, the drive machine for elevators further comprises arotation detector for detecting rotation of the drive sheave withrespect to the stationary shaft as a reference, detection differencecalculating means for detecting the difference between the rotation ofthe drive sheave detected by the rotation detector and the rotation ofthe drive sheave detected by the field magnetic pole detector, andanomaly determining means for determining the occurrence of an anomalywhen a value of the difference determined by the detection differencecalculating means exceeds a predetermined value. It is thereforepossible to early find an anomaly in the rotation detector, the fieldmagnetic pole detector, or the detected portion.

According to the ninth aspect of the present invention, on the basis ofthe eighth aspect, the drive machine for elevators further comprisesdrive control means for executing drive control of the motor inaccordance with results detected by the rotation detector and the fieldmagnetic pole detector, wherein when the value of the differencedetermined by the detection difference calculating means does not exceedthe predetermined value, the drive control means executes the controlwhile correcting an output value of the rotation detector in accordancewith the value of the difference. Accordingly, if there occurs a slightanomaly such as abrasion of a roller over time, the elevator cancontinue the operation for the present just by slightly correcting adetected value of the rotation detector. As a result, a rest time of theelevator attributable to the detection of anomaly can be minimized.

According to the tenth aspect of the present invention, on the basis ofthe first aspect, the drive machine for elevators further comprises arotation detector for detecting rotation of the drive sheave withrespect to the stationary shaft as-a reference, memory means for storingan output of the rotation detector in a corresponding relation to theposition detected by the field magnetic pole detector while the fieldmagnetic pole detector is detecting the field magnetic pole positionwith the rotation of the drive sheave, and drive control means forexecuting drive control of the motor in accordance with results detectedby the rotation detector and the field magnetic pole detector, whereinthe drive control means utilizes values stored in the memory means forphase control of electric power supplied to the armature. The accuracyin installation of the field magnetic pole detector or the correspondingdetected portion may affect phase control for one rotation of the drivesheave. Further, it is not always ensured that the pitch of the pair offield magnetic poles is divided so as to evenly cover one rotation.Storing values detected by each field magnetic pole detector and valuesdetected by the rotation detector makes it possible to implement thephase control with good accuracy by referring to the stored value andutilizing them in a combined manner for effective compensation.

According to the eleventh aspect of the present invention, on the basisof the first aspect, the drive machine for elevators further comprises arotation detector for detecting rotation of the drive sheave withrespect to the stationary shaft as a reference, and drive control meansfor executing drive control of the motor in accordance with resultsdetected by the rotation detector and the field magnetic pole detector,wherein the amount of change in value detected by the rotation detectoris determined at the start-up of the elevator while the field magneticpole detector detects one pair of the field magnetic poles, and thedrive control means executes phase control of the motor by setting theabove amount of change as a reference value of a phase signal for onepair of the field magnetic poles since then. When the values detected bythe rotation detector are neither sure nor definite with respect to thefield magnetic poles, the amount of change in value detected by therotation detector while the field magnetic pole detector detects thefirst pair of field magnetic poles is set as a temporary reference andis utilized in subsequent calculation for the phase control. Even if theposition in the field magnet is not known since then, the phasecalculation can be relatively precisely implemented. Once the drivesheave makes a turn under the drive control based on the temporaryreference, the subsequent phase control can be implemented with goodaccuracy by precisely recognizing the mutual positions detected by eachfield magnetic pole detector and the rotation detector during the turnas with the above tenth aspect of the present invention.

What is claimed is:
 1. A drive machine for elevators, comprising: anelectric motor including a rotatable drive sheave over which a maincable for hanging an elevator cage is wound, a stationary shaft forsupporting rotation of said drive sheave and bearing a load applied tosaid drive sheave from said main cable, a field magnet attached to saiddrive sheave and comprising at least one pair of magnetic poles, anarmature attached to said stationary shaft, facing said field magnet andconstituting part of said motor, detected portions comprising at leastone pair of convex or concave portions on or in the surface of saiddrive sheave at a pitch corresponding to the positions of magnetic polesof said field magnet for indicating the position of the magnetic poles,and a position detector disposed facing said detected portions fordetecting the position of said drive sheave by detecting whether saiddetected portion is opposite said position detector and, thereby, theposition of the magnetic poles of said field magnet that rotate togetherwith said drive sheave.
 2. The drive machine for elevators according toclaim 1, wherein said field magnet comprises a permanent magnet.
 3. Thedrive machine for elevators according to claim 1, wherein said positiondetector comprises a proximity sensor facing said detected portions. 4.The drive machine for elevators according to claim 1, wherein saidposition detector comprises a plurality of proximity sensors arranged ata pitch equal to {fraction (1/3+L )} of the pitch of a pair of saiddetected portions.